The paper describes the effect of dosage of polypropylene fiber on mixture consistency, flexural strength and compression strength and impact strength of fine-grained concrete. It was established that introduction of fiber leads to a certain decrease of consistency of the mixture, but bleeding are significantly decreases. It was found that the reason for the decrease in strength characteristics of concrete with addition of fiber can be related to heterogeneity of distribution of additive in material volume. Therefore, in order to increase the efficiency of use of fiber, necessary to use methods for preparing mixtures with fiber, which ensure a high uniformity of distribution of the additive in material. It was shown that micro-reinforcement increases impact resistance, even with insufficient quality mixing

Keywords: fine-grained concrete, propylene fiber, flexural strength , compressive strength, impact strength, heterogeneity